Band structure of ${\mathrm{Bi}}_2$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_8$ studied by angle-resolved photoemission

Angle-resolved photoemission measurement with synchrotron radiation has been performed on single-crystal ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$. Two dispersive bands intersecting the Fermi level midway between the Γ point and the Brillouin-zone boundary were observed. The other bands with higher binding energy are almost dispersionless in contrast with the band-structure calculation. The present experimental result indicates the existence of a Fermi surface and Fermi-liquid states in the high-$T_c$ superconductor as well as band renormalization due to the strong electron correlation.